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hp loss with a/c on?

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  • hp loss with a/c on?

    Exactly how much hp do you lose with the a/c on and why? I've heard any where from 10 - 15 hp.
    Hercules



    2008 Sunburst Metallic HHR LT

  • #2
    I heard 5HP. Not sure though.
    99 Black WS6
    99 Black Ski-Doo Mach Z
    94 Jeep Grand Cherokee

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    • #3
      I don't know what the loss is during regular driving, but it doesn't matter if it is on or off at WOT. The AC clutch disengages automatically if you romp on it. In fact, it may be better to leave it on so the fans cool the engine more if you're racing. Not an expert though. I use the AC to turn the fans on manually sometimes when the engine is running hot.

      Since the AC is belt driven, whatever load it creates on the engine can be measured in loss of HP. The harder it is to turn the compressor, the higher the loss.

      Sean
      1994 Z28, 6 spd, LE2 Heads, GM 1.6 RR, .026" head gasket, SLP: CAI-Headers (CARB legal)-ypipe-2 on the left-lightweight flywheel-short throw, Random tech cat, CF dual friction, LT-4 KM.

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      • #4
        Originally posted by DJ Taso
        Exactly how much hp do you lose with the a/c on and why? I've heard any where from 10 - 15 hp.
        I would bet its every bit of 15 HP. The A/C requires a compressor to be engaged by a clutch, which is driven by the belt. When you turn the A/C on, power is sent to engage a clutch on the compressor. WHen the clutch is engaged you will have a parasitic loss due to the crank turning the compressor; when the clutch is disengaged, it freewheels. However, the compressor kicks off at WOT, so in theory you will only lose power at part throttle, But, remember you will also lose power due to the fact that the engine will run hotter with the A/C on.
        96 WS6 Formula: Ram Air, 383 Stroker, Ported LT4 Heads and Manifold, 1.6 Crane Rollers, 58MM T.B., AS&M Headers, Borla Exhaust, Meziere Elec. H2O Pump, Canton Deep Sump Oil Pan, 100 HP OF TNT N2O!! , T56 Conversion w/ Pro 5.0 shifter, SPEC Stage 3 Clutch, Hotchkiss Subframe Conn., Lakewood Adj. Panhard Bar, Spohn Adj. LCA's, BMR Adj. T.A., Custom 12 bolt w/ 3:73's, Moser Axles, Eaton Posi, Moser Girdle
        11.6 @ 123mph (1.6 60' - getting there )

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        • #5
          Originally posted by N20LT4Bird
          But, remember you will also lose power due to the fact that the engine will run hotter with the A/C on.
          With the possible exception of really hot days (like today 90+), my observation has been that the engine stays cooler with the AC on, because the cooling fans are on longer (always?).

          The stock programming seems to let the engine get plenty warm before the fan(s) kicks on without AC.

          Sean
          1994 Z28, 6 spd, LE2 Heads, GM 1.6 RR, .026" head gasket, SLP: CAI-Headers (CARB legal)-ypipe-2 on the left-lightweight flywheel-short throw, Random tech cat, CF dual friction, LT-4 KM.

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          • #6
            When the A/C is on, the low speed fans are turned on, and running about 98% of the time I installed an LED indicator for the fan switch and always see the low speed side "on" when the A/C is running. There is only 1 time I recall not seeing it on. It was only for several seconds, then quickly turned on.
            94 Black T/A GT, Advanced Induction 355, 3200 stall, built 4L60E, Moser 9", Baer Brakes, Shooting for 11s...

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            • #7
              I can't realy trll if it looses power. I can still burn rubber in 3rd even with it on.


              LT4KM, 160' TS, MAF ends, TB-BP, GMPP 1.6 R/R, SLP CAI, LCA, Adj. tierod, BMR tower brace, 17x9"F/R, 275/40R17 GY F1 tires. WS6 Muffler, LS1 DS. 21mm rear sway bar. Soon to be LT4 heads, intake, & HOT cam

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              • #8
                I can definitely feel a loss of power with my a/c on and an M6. It's not a lot, but enough to notice it.
                Hercules



                2008 Sunburst Metallic HHR LT

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                • #9
                  Originally posted by DJ Taso
                  I can definitely feel a loss of power with my a/c on and an M6. It's not a lot, but enough to notice it.
                  Same here, if I am driving in fourth cruising at about 1800-1900 rpms and turn the AC on, I notice a very small hesitation. But like others have said at WOT I cant feel a difference, only around cruising and starts.
                  1996 Z-28 6 speed, Airfoil, K&N FIPK, Flowmaster muffler, Motive 3.73 gears, BBK shorty headers, cut-out, LS1 Driveshaft, no power options (Rare), Prothane tranny mount, MSD 8.5mm wires, Accel U-Groove Plugs, Chrome hurst short throw, TB Bypass, ES Torque arm mount, BMR subframe connectors (weld-in), Lt4 Knock Module, Descreened MAF, '02 SS wheels, Pioneer HU, MTX & JL amps, 2 12" JBL's, T-Top Conversion!

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                  • #10
                    During normal driving there is a noticable amount of HP loss with the AC on.
                    When I had my mustang GT there was no loss that I could detect, cant explain that one.
                    Are you guys sure the AC turns off when you mash the fun peddal?
                    1995 Z28 Convertible, 350ci LT1 73K miles M6.
                    Dyno results: 301.5 RWHP 326.7 RWTQ
                    Performance Mods 4.10 gears, AS&M CAI, MADZ28 tune, Borla catback, RK Sport mid-length headers, LT4 valve springs, CC pro mag 1.6 RR's, LT4 KM, MSD OVC wires, TB bypass, 160 t-stat, SLP clutch plate w/Kevlar dual friction disk, 52MM TB, TB air foil, 1LE aluminum driveshaft, ASP UD pulley, LS1 brakes w/ Hawk HPS pads, LCA's and PHB.

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                    • #11
                      The PCM really cuts off the electrical power to the compressor at WOT.
                      There are two ways to compensate the power loss when the A/C is on:
                      1) Increasing the fuel "expelled" by the injectors....F bodies
                      2) Increasing the RPM's thru a mechanical device or thru the PCM

                      My car is an auto, and I can feel a slightly loss of engine power but not so important to decrease the engine overall performance....but hey we can't drive with 100ºF or more !!!!outside the cockpit.....that means more of 110ºF inside the cockpit when the car has been parked a half an hour!!
                      I found an air extractor device in Pep Boys a few years ago. It hooks over the car window edge and works with a solar battery. So You close the windows with the device hooked and since the sun is present the extractor fan works.

                      Regards
                      Dochidalgo
                      97 A4 Pontiac Firebird Trans am with $everal mod$

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                      • #12
                        I notice a definite loss of power, but it's not huge. I rarely drive my car on sweltering days anyway. Scorching hot sun + black leather interior = Drive the Bravada.
                        SOLD: 2002 Trans Am WS.6 - Black on Black - 6 Speed
                        SLP Loudmouth Exhaust
                        17K Miles

                        2005 Acura TL - Silver on Black
                        Navigation - Surround Audio - Bluetooth

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                        • #13
                          Originally posted by Sean 94z28
                          With the possible exception of really hot days (like today 90+), my observation has been that the engine stays cooler with the AC on, because the cooling fans are on longer (always?).

                          The stock programming seems to let the engine get plenty warm before the fan(s) kicks on without AC.

                          Sean
                          Maybe its just my car. Both fans are programmed to come on early (like 180 or something) and ive got a 160 degree stat.. So, nothing changes with the A/C on....so I get about a 30-40 deg. increase with the A/C on a hot day. On a cooler day, not so much......but who uses the A/C on a cool day?.....its t-top weather.
                          96 WS6 Formula: Ram Air, 383 Stroker, Ported LT4 Heads and Manifold, 1.6 Crane Rollers, 58MM T.B., AS&M Headers, Borla Exhaust, Meziere Elec. H2O Pump, Canton Deep Sump Oil Pan, 100 HP OF TNT N2O!! , T56 Conversion w/ Pro 5.0 shifter, SPEC Stage 3 Clutch, Hotchkiss Subframe Conn., Lakewood Adj. Panhard Bar, Spohn Adj. LCA's, BMR Adj. T.A., Custom 12 bolt w/ 3:73's, Moser Axles, Eaton Posi, Moser Girdle
                          11.6 @ 123mph (1.6 60' - getting there )

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                          • #14
                            Well...the only way to find out is to fun the quarter with and without the ac on and see if your et is any different.
                            Greg W. in West Michigan
                            1992 Formula WS6-A/R Rims, Stock L05 swap, Former Abuse Victim
                            1983 Z28-Parts car- *Sold*
                            1984 Z28-305 HO Auto *Sold*
                            1986 Camaro-V-6 5Spd *Sold*
                            1984 Camaro-V-6 Auto *Sold*
                            <Motor out

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                            • #15
                              You can notice a lil kick and hesitation when you turn on the AC...I personally drive like a grandma...when I turn on the AC, I drive even easier. I feel like the engine almost hates having the AC on...

                              Christopher Teng

                              1999 · A4 · 3.73's · Auburn LSD · Whisper Lid · K&N · Pacesetter Headers/Y-pipe
                              Magnaflow Cat & Catback · MSD Coils/Wires · Bosch +4 Plugs · EGR Bypass
                              B&M SuperCooler · 160* Stat · Descreened MAF · SLP CAI · BMR STB & SFC
                              Strano Sways · Eibach Springs · Bilstein HD Shocks · Hawk-Pads · Brembo Blanks
                              Speedlines · Nitto 555s · Texas Speed Mail Tune

                              Lots of Weight Savings · Stubby Antenna · Corbeau TRS · Zaino · 273K

                              F-Body Dirty Dozen

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